E39 Aux Fan Service - READ ON

[PENER]

as many of you know, auxiliary fan failure is one of many weak points on most bimmers. just to remind, it's the electric fan mounted in front of the A/C condenser (that is located in front of the radiator) that sometimes makes our cars sound like an airplane during acceleration.

the aux fan is always on (low speed) whenever A/C compressor is on, to cool off the refrigerant flowing through the condenser (using A/C without properly functioning aux fan can cause compressor failure). when it's very hot, the fan may go into medium or rarely high mode, which really sound like an airplane, to provide some extra cooling for the cooling system.

additional info: the connector for the fan consists of four wires:
brown-ground
blue-12v direct to fan, high mode
red-12v through single resistor to fan, med mode
black-12 through both resistors (in series) to fan, low mode

you can notice the first problems with the fan if it's not coming on when A/C compressor is on. the possible reasons of this are:
-bad fuses: #7,20,22 or 75, the last one being under and behind the glove box comp.
-failed resistor(s)
-failed radiator temp switch
-failed fan motor
(-rarerly failed relay)

most often it is either bad resistor pack or fan. it's worth mentioning that a failed resistor may often cause the fuses to blow. the reason for that is that with failed resitors the fan is not working on low speed and on the occasions it is kicking into high there is too much current draw.

to check whether it's the mulfunctioning resistor, (assuming all fuses are OK) you can just jump pins at the temp switch, or connect 12v DC directly to the fan connector (brown-ground, blue-12v positive). if the fan kicks in high mode, the problem is the resistor pack ($50-60).
if the fan is not working at all, the second method (direct 12v) will tell you whether the fan motor is the culprit.

most online vendors want almost $60 for the resistor packs and the fan motor alone is a whooping $200. preety steep, considering the entire fan assembly costs $300, though seeing the size of the motor and how powerfull it is, no wonder it costs so much.
below is the pic of the fan motor from one of my favorite online vendors, charging around $190 for it


however, I have been able to spot a tremendous deal for the very same motor at Autozone. the same fan (SIEMENS PM9047) they sell for ONLY $82!!!
below it the fan motor I ordered from AutoZone

as you can see, it's the very same fan, and actual replacement part for our cars. comes terminated with the prongs that slide into the connector and even has a part of the blue wire stripped in place where resistor packs connect to it

some pics of my old fan and new replacement



(I'd like to add here, that upon removal of the old fmotor, I found it to be still spinning with 12v put to it, although it did not work during the earlier tests. however many owners can confirm similar results with their old units. but now, knowing that you can get the new motor for only $82, it's no brainer...)


replacement of the fan resistor pack or entire fan assembly requires the bumper to be removed first together with both headlights and the (kidney) cowl. sorry for the crappy pic (low light conditions) BTW in case someone wonders where is the Secondary Air Pump (bottom left corner of the pic), it's been replaced with new type pump and retrofitted under the hood.


good luck

[jbiel]

Being in Florida and using the A/C constantly, the aux fan in my 99 540i is LOUD, I am wondering if the fan *should* be that loud at all times or is it just because of the work it's doing for the heat / A/C system.

I'd like to replace it because its so loud, but if even a new one will be that loud, I won't even worry about it.

Great write up though.

[PENER]

with the engine running the fan noise is hardly noticable unless it kicks in into high. and since the noise is mostly coming from the fan blades cutting through the air, replacing the motor could only worsen the matter, as the new one would pull even stronger.

[franka]

Originally Posted by jbiel

Being in Florida and using the A/C constantly, the aux fan in my 99 540i is LOUD, I am wondering if the fan *should* be that loud at all times or is it just because of the work it's doing for the heat / A/C system.

I'd like to replace it because its so loud, but if even a new one will be that loud, I won't even worry about it.

Great write up though.

Like Pener said it's the blades cutting thru the air that makes the sound, not the motor.

The aux fan's function is to move a lot of air thru the radiator on an "as needed" basis. If it's on it is needed.

Therefore I would not recommend tampering with it to decrease the noise.

[oekundar]

Great write-up!

[jbiel]

Thanks for the responses guys, I just wanted to clear my mind of thinking I had a bad Aux Fan.

[Hotswimmer]

PENER,

Really nice write-up. Can you also post this to the E39 FAQ so it stays right up front where we can find it?

Thanks!!!

[PENER]

thanks guys.

feel free to post links to this thread.

I don't really see anything big in this thread. it's mostly summs up the issues with the fan. the real reason I post it, was to let everyone know that there is no need to spend $200 for the fan motor when there is one place (located all over the states) that sells it for $80.

[SleekBMW]

I am actually going to go buy all the parts for this, but Autozone cant seem to find it without a part number, and i gave them the part number in the fan motor above. they didnt find it.

Anyhow, where can i purchase the resistor packs? Also, to get to fuse number 75, do i have to remove the glove box or just kneel under my glove box?

what is the part # for the resistor packs?

[BlackSapphire]

My fan was noisy as hell but I didn't realize how much so until the dealer replaced it. They were trying to fix a complaint I had regarding transmission noise and they thought maybe that's what I was hearing. Once they replaced the aux fan, THEN they could hear the noise I was complaining about.

[e39dream]

great write-up! I bookmarked it for future reference. I will be posting a link to this in my cooling system thread up top, thanks Pener!

[SleekBMW]

am i supposed to buy 2 resistor packs from bav auto or one?

BTW i just purchased the fan motor, and i want everyone to know
that at autozone, that is listed as Radiator Fan motor with part # PM9047, make sure they put PM or spark plugs will come up, i had to travel to 3 autozones before they figured that out, i carried my laptop showing them until i found a younger dude in his 20's hes like, ok here you go in like 1 min. so FYI make sure they put in PM9047

[SleekBMW]

Quick question, what is a pick that is needed to remove the bumper?

[e39dream]

I know theres a special puller tool for the plastic push in rivets but I don't think it's needed for a one time removal/install provided you buy a hand full of new rivets to put it back together with. They are the things under the bumper trim with the centers that pull out, making the fastener smaller in diameter and easier to pull out. It's simple enough to pull the center pins with needle nose pliers and pop the fasteners with a flat screwdriver or small scraper.

[e39dream]

it's either part 22 or 31 on this diagram, get 10 of each to be safe lol.
the parts counter at BMW dealerships have these on hand.

http://www.realoem.com/bmw/showparts...53&hg=51&fg=15

[NY550i]

Can the motor be making noise or just the blades?
Im actually having issues with my aux fan... it is way to loud! once the car warms up to normal temperature the aux fan goes on and the car idles with a loud fan

I took the car to a indy and they replaced the whole aux fan with a new one and it still made noise so they said the fan might be defective so they will replace it with another new unit... im starting to believe the problem is not in the fan but something else

[Dan]

Originally Posted by Hotswimmer

PENER,

Really nice write-up. Can you also post this to the E39 FAQ so it stays right up front where we can find it?

Thanks!!!

+1

greg, replicate his up there!

[SleekBMW]

Originally Posted by e39dream

it's either part 22 or 31 on this diagram, get 10 of each to be safe lol.
the parts counter at BMW dealerships have these on hand.

http://www.realoem.com/bmw/showparts...53&hg=51&fg=15

lol, i have a tendency to mess up...im going to get 20. of each

Originally Posted by e39dream

I know theres a special puller tool for the plastic push in rivets but I don't think it's needed for a one time removal/install provided you buy a hand full of new rivets to put it back together with. They are the things under the bumper trim with the centers that pull out, making the fastener smaller in diameter and easier to pull out. It's simple enough to pull the center pins with needle nose pliers and pop the fasteners with a flat screwdriver or small scraper.

So far this is what i understand, and i appreciate you letting me know that you will help me do this, but i have to do this urgently as i have to drive down to St. Louis this friday.

so i will take pics and make a DIY but this is what i understand so far please correct me if im wrong
tools needed - I have a regular 3/8 drive wrench with a 1/4 adapter
8mm socket
13mm socket
10mm socket
T45 Torx from Murrays @ 6 dollars came with 40-45-50.
needle nose pliers
5-4' extensions (just in case)
a pack of cigarettes. (may come in handy if im frustrated)

1- disconnect battery
2- remove the screws that connect the bumper each side of the wheel well
3- remove screws at the fog light grill
4- go under the bumper and use the needle nose pliers and PULL those picks out as hard as i can.
5- after fog lights etc have been removed pull the foglight grill out
6- find the place where the T45 torx and unscrew that piece
7- pull bumper off
8- remove they kidney shroud
9- remove the auxilary fan shroud
10- loosen away fan motor
11- clean fan and condensor etc
12- screw in new motor
13- unplug old resistor pack and plug in new one
14- follow steps and put the whole thing back together again.

Now i will have a function auxilary fan

But i have a question, what the hell is that thing that is circled in red? and howdo i get it off?



pics courtesy of BMWtips.com

thanks for all your help, i will make a DIY for this with LOTS of pics.

[SleekBMW]

bump

[e39dream]

hey sleek thats the air inlet to the air filter- it snakes into and behind the bumper support- yours will be a little different than pictured because its a 6 cylinder. As for how it comes off- you may have to pioneer a little That whole snake looking thing is in the extra parts pile of my car

[SleekBMW]

thanks man! i appreciate it, lets see how this goes!

[SleekBMW]

Just in case Greg didnt get my Email,
How do you remove the fan from the motor?
how do you wire the new wires into it powering the fan?
The motor ONLY came with 2 wires.


Anything else i will post
Thank you ALL for your help..Actually for this i thank Mark and Greg.

[SleekBMW]

bump

[NNY528I]

Any one know off the top which wire in the resistor pack goes to which pin in the connector. I was hopped up on coffee after a late night run and failed to note there positions when i pulled them out. The 2 in question are the black and the black and red.

Thanks,

[md80boy]

what is the number of the packs and where can we buy them?